Method and means for disposal of waste gas



Sept. 23, 1969 J. 1.. MAHER METHOD AND MEANS FOR DISPOSAL OF WASTE GAS 5 Sheets-Sheet 1 Filed Oct. 19, 1967 INVENTOR. JOSEPH L. MAH R ATTORNEY p 23, 1969 J. L. MAHER 3,468,238

METHOD AND MEANS FOR DISPOSAL OF WASTE GAS Filed Oct. 19, 1967 5 sheets-Sheet 2 INVENTOR. JOSEPH L.

ATTORNEY J- L. MAHER METHOD AND MEANS FOR DISPOSAL OF WASTE GAS 5 Sheets-Sheet 3 Sept. 23, 1969 Filed Oct. 19, 1967 'INVENTOR. JOSEPH L. MA HER ATTORNEY 3,468,238 METHOD AND MEANS no nisrosAL or WASTE GA US. Cl. 98-1 Claims ABSTRACT OF THE DISCLOSURE A stack is disclosed with a fan mounted at its lower end. Waste gas to be disposed of is ejected from conduits branching from a manifold below the fan. Flow diverters and valves are mounted on the ends of the branch conduits to control the gas passed up into the fan.

BACKGROUND OF THE INVENTION Field of the invention-US. Patent 3,318,223 advances the broad theory that gas distributed at predetermined positions in a horizontal plane below a fan will be mixed with air into a non-hazardous combination. The present invention relates to control of the quantity of gas released from each position and the direction given the released gas.

Description of the prior art-It is now acceptable to dispose of the large quantities of waste gas, from petroleum production, by first mixing the gas with sufficient air to dilute it below a combustible concentration. For pure methane, the lower limit of combustion is approximately 5% gas by volume. The lower limit decreases to 3.22% for ethane. For natural gas having methane as the major component, dilution with air should be carried down to a gas concentration of approximately 3%.

In the art practiced under US. Patent 3,318,223, the branch conduits either do not release gas uniformly or there is material variation in the turbulence created by the large fan over the predetermined positions. In either event, non-uniformity of the gas dispersion over the cross section of the stack has been noted. Additionally, the upward jetting of gas from the exits of the branch conduits apparently loads the fan motor. The release of gas, in both quantity and direction, must be controlled to increase the speed and uniformity of mixing and decrease loading on the fan motor.

SUMMARY OF THE INVENTION It is a principal object of this invention to divert gas from vertical discharge beneath a fan in the direction of fan rotation.

Another object is to separately control the quantity of gas discharged from each of a plurality of positions beneath a fan to produce uniform distribution of gas above the fan.

The invention contemplates a vertical stack structure with a fan rotating in a horizontal plane at the lower end of the stack. A manifold conduit brings waste gas beneath the fan, and branch conduits extend upward from the manifold to a horizontal plane beneath the fan. Diverters mounted on the ends of the branch conduits direct the gas in the direction of fan rotation. The result is a swirling of the gas streams beneath the fan which initiates mixing of the gas and air flowing up to the fan. Also, the force of the gas impingement on the fan is reduced. Additionally, a valve structure over the discharge end of each branch conduit controls the amount of the total gas discharged from each branch. This control of quantity discharge can be varied to obtain a uniform distribution over the cross section of the stack.

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Other objects, advantages and features of this invention will become apparent to one skilled in the art upon consideration of the written specification, appended claims, and attached drawings, wherein:

FIG. 1 is an elevation of an off-shore production platform on which is a dispersal unit including the present invention is embodied;

FIG. 2 is a sectioned elevation of the dispersal unit;

FIG. 3 is a sectioned and perspective elevation of the lower portion of the unit; and

FIG. 4 is a sectioned and perspective elevation of a housing unit on the end of a branch conduit.

REDUCTION TO PRACTICE Since the filing of US. Patent 3,318,223, units built under the concepts disclosed and claimed therein have continued to gain acceptance by major oil producing companies having off-shore installations. There are many indications that the unit will enjoy an increasing demand for the foreseeable future.

In US. Patent 3,318,223, it was stated that satisfactory mixing took place in a very short length of travel by the mixture from the fan discharge. However, continued testing evidenced this statement requires some qualification. Certain sizes of fan, stack and gas manifold have produced mixtures not satisfactorily uniform over the cross-section of the stack discharge. Further, although the velocity of the discharged gas may be controlled to eliminate the resonance referred to in this patent, loading of the fan motor from impingement of the vertically directed gas on the fan blades has been noted.

It was discovered that uniformity in the mixture can be produced by controlling the amount of gas released from each branch conduit connected to the waste gas manifold. The relative amounts of gas discharged from the branches can be tuned so to speak. When properly exerted, this control results in a uniformity of the gas-air mixture which maintains the mixture non-hazardous.

Further, diversion of the gas discharge direction from the vertical reduces the load on the fan motor. If the diversion is in the direction of fan rotation, a degree of pre-mixing of the air and gas will be brought about before the fan blades are reached. This arrangement, alone,

will promote uniformity to the mixture at the top of the stack.

OVERALL PRODUCTION INSTALLATION The characteristics of each well product requires particular equipment at the well head. FIG. 1 is established to illustrate a production location off-shore as typically associated with a platform 1 extending up from the bottom. On this platform has been generally indicated various pieces of production equipment, including the unit 2 embodying the present invention.

The well, or wells, is drilled below the surface of the water. Conduits gather the well production to the platform. After the initial processing, the products may be conducted to shore facilities or storage on the platform. Many and varied arrangements have been used and considered. However, the waste gas at this off-shore location has been a problem.

It has been customary to burn Waste gas. On land this burning equipment is not difficult to provide, sufficiently remote from the production facility to eliminate the hazard. But how about these off-shore installations? If the burning is removed a safe distance from platform 1, a separate platform for this special function could be extremely expensive. In water hundreds of feet deep a simple platform could cost many hundreds of thousands of dollars. The present invention provides a process and apparatus for safely disposing of this waste gas right on the production platform 1 itself. Unit 2 receives this waste gas, mixes it with air and discharges the mixture high in the air. Without being burned, the gas is rendered harmless to the production facility and personnel.

GENERAL STRUCTURAL ARRANGEMENT OF UNIT 2 Referring specifically to FIG. 2, the waste gas dispersal unit, embodying the present invention, is illustrated as a skid-mounted stack 3 mounted to extend vertically up into the air. Stack 3 is shown here as supported by structural members 4 which extend up from a skid 5 base to support the lower end 6 of the stack well above the horizontal plane of the skid. A flared skirt 7 extends downward from the periphery of the lower end 6 of stack 3. A manifold conduit 9 brings the waste gas to the stack and also forms a convenient structural mount for a motor 10 which is linked to fan fiades 11 to rotate them at the lower end 6 of stack 3. Air flows up under flare skirt 7 and into rotating fan blades 11, along with the waste gas from conduit 9. The mixing of these two fluids takes place quickly, and is completed in only a short distance of travel above the fan blades 11. The mixture is then forced upward to discharge from the upper end 12 of stack 3.

Branch conduits 13 connect to manifold conduit 9 and extend upward to terminate in a common plane which is parallel to the plane of fan blade rotation. Further, the discharge ends of conduits 13 are spaced on a circle about the center of blade rotation. On each of the discharge ends of conduits 13 is mounted a housing 14. As will be disclosed more clearly in FIG. 3, the structure of each housing 14 controls the release of Waste gas from each branch conduit 13 to carry out the objects of the present invention.

FAN AND DISTRIBUTION SYSTEM FIG. 2 and FIG. 3 are to be taken together to disclose the spatial relation between the housings 14 and fan blades 11. Rotation of the fan is indicated as clockwise and the gas discharged through each housing 14 is also directed clockwise. This arrangement eliminates impingement of the gas on the blades 11 and causes the gas to be swirled before blades 11 are reached. A degree of premixing of gas and air takes place below the blades, increasing the efficiency of mixing. The mixture becomes uniform well before its discharge from the top of the stack.

Each housing 14 is mounted on the top of a branch conduit 13. The gas from the branch conduit is received into the housing 14 and diverted from the vertical. More specifically, housing 14 is provided with a top plate which extends at some angle to the horizontal. Plate 15 determines the amount of diversion from the vertical. Side plates 16 and 17, together with the top and bottom plates, form a funnel shape which diverges from the outlet of branch conduit 13 to further dispersion of the diverted gas before it is actually discharged and mixed with the air flowing up under skirt 7.

HOUSING 14 The dispersed gas discharged from the housings 14 should flow smoothly into a swirling pattern beneath the fan. It may be found that each housing 14 outlet should be directed to one side of the back of the housing 14 in front of the discharge. Impingement of the gas streams on the housings 14 is thereby avoided.

A valve element 18 is mounted in association with each branch conduit outlet. In FIG. 4, this valve element can be seen in the simple form of a damper pivoted on the bottom plate of housing 14. Other valve arrangements are obviously available, but all valve arrangements are to merely control the amount of gas discharged from the outlet of their branch conduits 13.

In operation, each valve element 18 can be set individually to release the amount of gas from its branch conduit 13 which will result in uniform distribution of the gas across the cross-sectional area of stack 3. Each valve element may have a different setting. The settings can be ascertained empirically in order to tune the entire unit to deliver with desired uniformity. The result of both diversion, dispersion and controlled release is efficient mixing of the waste gas with air to a uniform mixture discharged from the top of stack 3.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obviously and which are inherent to the method and apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. A method of dispersing waste gas of petroleum production through a vertical stack, including:

conducting waste gas of petroleum production to a plurality of predetermined positions in a horizontal plane at the lower end of the stack,

directing the portion of waste gas released at each of the positions in the horizontal plane at a predetermined angle to the plane,

flowing air through the plane from which the gas is released,

creating a perdetermined turbulence above the plane to form a mixture which is non-hazardous, and

discharging the mixture from the top of the stack.

2. The method of claim 1 wherein:

the portion of waste gas released at each of the positions in the horizontal plane is predetermined in quantity to produce a uniformity of the mixture over the stack cross-section.

3. A method of dispersing waste gas of petroleum production through a vertical stack, including:

conducting waste gas of petroleum production to a plurality of predetermined positions in a horizontal plane at the lower end of the stack,

releasing a predetermined portion of the waste gas from each of the positions in the horizontal plane,

flowing air through the plane from which the gas is released,

creating a predetermined turbulence above the plane to form a mixture which is non-hazardous, and

discharging the mixture from the top of the stack, the mixture being uniform because a predetermined quantity of gas is released at each position.

4. A dispersal unit for waste gas of petroleum production, including:

a vertical stack,

a source of waste gas of petroleum production to be dispersed,

'a manifold conduit with branch conduit outlet means, the manifold conduit connected between the source and stack, the branch conduit outlet means arranged in a predetermined pattern in a horizontal plane at the lower end of the stack,

a valve means mounted on each branch conduit outlet means to control the amount of the waste gas released from each branch outlet, and

fan blades mounted to rotate in a plane above and parallel to the plane in which the waste gas is released to create a zone of turbulence above each branch conduit outlet means in which the gas and air References Cited will mix and discharge as a uniform non-hazardous UNITED STATES PATENTS mixture from the upper end of the stack. 5. The dispersal unit of claim 4, including: 3,318,223 5/1967 Maker 98 1 a diverting means mounted on each branch conduit FOREIGN PATENTS outlet means to direct the waste gas released at a predetermined angle to the plane and in the direction 830715 5/1938 France Of the fan b ade ro at on- LLOYD L. KING, Primary Examiner 

